package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;
import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

/**
 * @Title: IPersistence
 * @Description:
 * @Author: Wenfeng Cheng
 * @Date: 2020-11-28 11:41
 * @Version: 1.0.0
 */
public class SimpleExecutor implements Executor{

    private Connection connection = null;

    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1、获取链接
        connection = configuration.getDataSource().getConnection();
        //2、获取sql  select * from user where id = #{id} and username = #{username}
        //   转换sql  select * from user where id = ? and username = ?
        BoundSql boundSql = getBoundSql(mappedStatement.getSql());
        //3、创建与处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //4、参数处理
        //获取到参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }

        //5、执行
        ResultSet resultSet = preparedStatement.executeQuery();

        //6、封装返回结果集
        String resultType = mappedStatement.getResultType();
        Class<?> resultTypeClass = getClassType(resultType);
        List<E> list = new ArrayList<>();
        while(resultSet.next()){
            E o = (E)resultTypeClass.newInstance();
            ResultSetMetaData metaData = resultSet.getMetaData();
            for (int i=1; i<=metaData.getColumnCount(); i++){
                //字段名
                String columnName = metaData.getColumnName(i);
                //字段值
                Object value = resultSet.getObject(columnName);
                //使用反射或内省，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName,resultTypeClass);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            list.add(o);
        }
        close();
        return list;
    }

    @Override
    public int update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        //1、获取链接
        connection = configuration.getDataSource().getConnection();
        //2、获取sql
        BoundSql boundSql = getBoundSql(mappedStatement.getSql());
        //3、创建预处理对象
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        //4、参数处理
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramtertypeClass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for (int i = 0; i < parameterMappingList.size(); i++) {
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            //反射
            Field declaredField = paramtertypeClass.getDeclaredField(content);
            //暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }
        //5、执行
        int count = preparedStatement.executeUpdate();
        close();
        return count;
    }

    @Override
    public void close() throws SQLException {
        connection.close();
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType != null){
            Class<?> aClass = Class.forName(paramterType);
            return aClass;
        }
        return null;
    }

    /**
     * 完成对#{}的解析工作： 1、将#{}使用？替换  2、将#{}里面的值进行存储
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        //标记处理类：配置标记处理器来完成对占位符的解析工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{", "}", parameterMappingTokenHandler);
        //解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        //#{}里面解析出来的参数名称
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }
}
